Linear ultrasonic motor and lens apparatus and image pickup apparatus using the same

ABSTRACT

A linear ultrasonic motor includes a vibrator having a piezoelectric element, a movable part applying a pressing force to the vibrator and bringing the vibrator into pressed contact with a base part, a cover part being fixed to the base part, a rolling part being rollably held between a movable guide part of the movable part and a cover guide part of the cover part, and a body to be driven having a transmission member that is pivotably supported and able to move only in the movable direction. The transmission member includes a bias part that abuts on a transmission part of the movable part and applies a biasing force of biasing the movable part to the rolling part to the transmission part. The rolling part is held by a resultant force of the pressing force or a reaction force of the pressing force, and the biasing force.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ultrasonic motor, and particularlyrelates to a linear driving type of ultrasonic motor (hereafter referredto as linear ultrasonic motor).

2. Description of the Related Art

In a linear ultrasonic motor, conventionally, a high-frequency voltageis applied to a piezoelectric element, and thereby the piezoelectricelement vibrates a fixed ultrasonic vibrator. The vibration of theultrasonic vibrator drives a sliding member which is pressurized by theultrasonic vibrator. Various ideas are considered for achieving a linearultrasonic motor which can keep a high output even with a small size andenhances driving efficiency.

For instance, in a linear ultrasonic motor disclosed in Japanese PatentApplication Laid-Open No. 2005-99549, a transmission unit between anultrasonic vibrator and a member to be driven is arranged in a directionperpendicular to an optical axis, in other words, perpendicularly to adriving direction.

However, in the above described linear ultrasonic motor disclosed inJapanese Patent Application Laid-Open No. 2005-99549, it has beennecessary to increase a pressurization force of a bias member against avibrator, in order to prevent a follow-up delay in the drivingdirection. However, there has been a problem that when thepressurization force is excessively large, an equalizing property for atransmission member decreases.

An object of the present invention is to provide a linear ultrasonicmotor which can efficiently transmit a driving force to a body to bedriven.

SUMMARY OF THE INVENTION

The linear ultrasonic motor of the present invention has the followingconstitution.

A linear ultrasonic motor includes a vibrator, the vibrator having apiezoelectric element; a movable part, the movable part applying apressurization force to the vibrator and bringing the vibrator intopressurized contact with a base part; a cover part, a cover part beingfixed to the base part; a rolling part being rollably held between amovable guide part of the movable part and a cover guide part of thecover part, the movable guide part extending in a movable direction andthe cover guide part extending in the movable direction; and a body tobe driven, the body to be driven having a transmission member that ispivotably supported and being able to move only in the movabledirection. The transmission member includes a bias part that abuts onthe transmission part of the movable part and applies a biasing force ofbiasing the movable part to the rolling part, to the transmission part.The rolling part is held by a resultant force of the pressurizationforce or a reaction force of the pressurization force, and the biasingforce.

The present invention can provide a linear ultrasonic motor which canefficiently provide a driving force to a body to be driven.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a linear ultrasonic motor according to a firstexemplary embodiment of the present invention.

FIG. 2 is a perspective view of a linear ultrasonic motor to which alens retention frame is connected, according to the first exemplaryembodiment of the present invention.

FIG. 3 is an exploded perspective view of the linear ultrasonic motor towhich the lens retention frame is connected, according to the firstexemplary embodiment of the present invention.

FIG. 4A is a sectional view of an essential part of the linearultrasonic motor to which the lens retention frame is connected,according to the first exemplary embodiment of the present invention.

FIG. 4B is a sectional view of an essential part of the linearultrasonic motor to which the lens retention frame is connected,according to the first exemplary embodiment of the present invention.

FIG. 5 is a sectional view of a lens barrel which has a linearultrasonic motor mounted thereon according to the first exemplaryembodiment of the present invention.

FIG. 6 is a sectional view of an essential part of a linear ultrasonicmotor which is a second exemplary embodiment of the present invention.

FIG. 7 is a sectional view of an essential part of a linear ultrasonicmotor which is a third exemplary embodiment of the present invention.

FIG. 8 is a side view of a linear ultrasonic motor according to a fourthexemplary embodiment of the present invention.

FIG. 9 is an exploded perspective view of the linear ultrasonic motoraccording to the fourth exemplary embodiment of the present invention.

FIG. 10 is a sectional view of an essential part of the linearultrasonic motor which is the fourth exemplary embodiment of the presentinvention.

DESCRIPTION OF THE EMBODIMENTS

Preferred exemplary embodiments of the present invention will now bedescribed in detail in accordance with the accompanying drawings.

Incidentally, a linear ultrasonic motor which is unitized as an actuatorthat drives a lens barrel and the like of a digital camera will bedescribed below, as an example. However, the application in which thepresent invention is used is not limited to this example.

In addition, in the present specification, the same member in the figureis designated by the same symbol, and a moving direction of a movablepart which will be described later with respect to a base part isdefined as an X-axis (movable direction), and a normal direction of acontact part of a vibration plate included in the movable part isdefined as a Z-axis, in order to clarify the structure of the linearultrasonic motor and the movement thereof. In addition, a directionperpendicular to both the X-axis and the Z-axis is defined as a Y-axis.The directions of the axes in each figure are illustrated in the figure,but are not limited to these directions.

Exemplary Embodiment 1

FIG. 1 is a side view of a linear ultrasonic motor 100 when viewed fromthe Y-axis direction, which is a first exemplary embodiment of thepresent invention, and the movable part is in a middle position.

FIG. 2 is a perspective view of the linear ultrasonic motor 100 to whicha lens retention frame has been connected, and the movable part is in amiddle position.

FIG. 3 is an exploded perspective view of the linear ultrasonic motor100 to which the lens retention frame is connected.

Firstly, the structure of the linear ultrasonic motor 100 will bedescribed below with reference to FIG. 1, FIG. 2 and FIG. 3.

The linear ultrasonic motor 100 in the present exemplary embodiment hasa longitudinal axis in an X-axis direction, and is formed of each memberwhich will be described below. A vibration plate 101 has a piezoelectricelement 102 fixed thereon by a well-known adhesive or the like, and thepiezoelectric element 102 excites a vibrator 103 by voltage appliedthereto. Incidentally, a method for bonding the vibration plate 101 tothe piezoelectric element 102 is not limited as long as the vibrationplate 101 is bonded to the piezoelectric element 102. The vibrationplate 101 further includes a contact part 101 a, and the contact part101 a comes in contact with a contact base member 115 which will bedescribed later, under a pressurized contact condition that entailspressurization. The vibrator 103 is formed of the vibration plate 101and the piezoelectric element 102. When an AC voltage is applied to thepiezoelectric element 102 in a state in which the vibration plate 101and the piezoelectric element 102 are bonded to each other, a resonancephenomenon occurs in each of a longitudinal direction and a transversedirection of the vibrator 103. As a result, ellipsoidal motion occurs inthe contact part 101 a of the vibration plate 101. A direction ofrotation and an ellipse ratio of the ellipsoidal motion areappropriately changed by changing a frequency and a phase of the voltagewhich is applied to the piezoelectric element 102, and thus a desiredmovement can be obtained.

A vibrator support member 104 has a convex shape in the Z-axis directionof a YZ cross section, and includes a through hole for receiving aspring 108 and a spring retention member 107 therein, and a transmissionpart 104 a that is engaged with a pivot member 119 which will bedescribed later. The spring retention member 107 has a face forreceiving and holding one end of the spring 108, and the back side ofthe face comes in surface contact with a pressurization plate 105. Theother end of the spring comes in contact with a spring keep plate 109,and the spring keep plate 109 can be fitted into the through hole of thevibrator support member 104. In the through hole, the spring 108 is heldby the spring retention member 107, and is interposed between thepressurization plate 105 and the spring keep plate 109. Thereby, thespring 108 can freely expand and contract, and applies a pressurizationforce to the Z-axis direction. In addition, the pressurization plate 105has two projecting portions on a face of a side which receives thespring retention member 107, in a direction parallel to the normal lineof the face. The two projecting portions are received by the holes whichare provided on the vibrator support member 104, respectively. Themovement to a direction other than the Z-axis direction is limited bythis structure, and the pressurization force is efficiently transmittedto other members. In the present exemplary embodiment, thepressurization plate 105, the spring retention member 107, the spring108 and the spring keep plate 109 constitute a pressurization member,and the centers of gravity of each component can be connected by astraight line parallel to the Z-axis.

An elastic member 106 is arranged between the piezoelectric element 102and the pressurization plate 105.

A moving plate 110 has a fitting hole having an approximatelyrectangular shape and three movable guide parts 110 a, 110 b and 110 cof V-shaped grooves, and the projecting portion of the vibrator supportmember 104 is fitted into the fitting hole of the moving plate 110. Themovable guide parts 110 a, 110 b and 110 c of the V-shaped groovesextend with a predetermined length in the X-axis direction.

On the other hand, a cover plate 112 which functions as a cover memberalso has a hole having an approximately rectangular shape and threecover guide parts 112 a, 112 b and 112 c of V-shaped grooves that extendwith a predetermined length in the X-axis direction, and a projectingportion of the vibrator support member 104 is fitted into the hole.Spherical rolling members (rolling balls) 111 a, 111 b and 111 c whichcorrespond to a rolling part is rollably interposed between the coverguide parts 112 a, 112 b and 112 c of the V-shaped grooves and themovable guide parts 110 a, 110 b and 110 c of the V-shaped grooves,which correspond to the cover guide parts, respectively. Thus, themovable guide part provided in the moving plate of the movable part, thecover guide part provided in the cover plate of the base part, and therolling part rollably interposed between these guide parts constitute aguide mechanism. Incidentally, the shape of the movable guide parts 110a, 110 b and 110 c and the cover guide parts 112 a, 112 b and 112 c isnot limited to the V-shaped groove, and may be another shape as long asthe rolling part can be rollably interposed between the movable guidepart and the cover guide part. The vibrator support member 104 and themoving plate 110 are structured so as to be capable of relatively movingin the X-axis direction with respect to the cover plate 112, withoutcausing rattle.

The linear ultrasonic motor 100 further includes a base member 114. Thebase member 114 has a concave shape on an XZ plane, and has side wallsin both sides of the X-axis and a fixed part formed of one part thereof.The fixed part has screw holes, which face the screw holes of the coverplate 112, respectively. The cover plate and the base member 114 arefixed to each other by a screw 113, but a fixing method is not limitedas long as the cover plate and the base member are fixed to each other.In addition, the contact base member 115 is fixed to the bottom facepart of the base member 114 from the lower side of the Z-axis by anot-shown screw or the like. The contact base member 115 comes incontact with the contact part 101 a of the vibration plate 101, and theellipsoidal motion which is generated in the vibrator 103 is convertedinto a driving force of the movable part by the friction therebetween.The movable part can move forward and backward in the X-axis directionby the driving force. Incidentally, a method for fixing the base member114 to the contact base member 115 is not limited as long as the basemember is fixed to the contact base member. In the present exemplaryembodiment, the movable part is formed of the vibrator 103, the elasticmember 106, the pressurization plate 105, the vibrator support member104, the spring retention member 107, the spring 108, the spring keepplate 109 and the moving plate 110. In addition, a base part is formedof the cover plate 112, the screw 113, the base member 114 and thecontact base member 115.

Hereinafter, the pressurization force which is generated in thepressurization member will be described below. The spring 108 appliesthe pressurization force to the pressurization plate 105 through thespring retention member 107. The pressurization force furtherpressurizes the vibrator 103 to the contact base member 115 through theelastic member 106, and the vibrator 103 is pressed against the contactbase member 115. The contact part 101 a of the vibration plate 101 comesin contact with the contact base member 115 in a state of beingpressurized against the contact base member. On the other hand, areaction force of the pressurization force caused by the contact basemember 115 is received by the cover plate 112 through the rolling part.When the voltage is applied to the piezoelectric element 102 under thispressurized contact condition, the resonances in each of the X-axisdirection and the Y-axis direction occur in the vibrator 103, and thetip of the contact part 101 a causes the ellipsoidal motion. As aresult, the movable part can move forward and backward in the X-axisdirection.

Hereinafter, the connection between the ultrasonic motor 100 and thelens retention frame which holds an optical lens will be describedbelow.

In FIG. 2 and FIG. 3, a lens G2 is fixed to a lens retention frame 116which functions as a body to be driven, and the lens retention frame 116constitutes a part of the lens unit of a digital camera or the like. Thelens retention frame 116 has a fitting hole 116 a into which a guide bar117 is relatively slidably and freely fitted. In addition, an engagingpart 116 b is relatively slidably and freely engaged with a steady bracebar 118, which prevents the rotation of the lens retention frame 116around the guide bar 117. The lens retention frame 116 further has apivot member holding part 116 c formed therein which is engaged with apivot member and functions as a pivotably movable transmission member,and a well-known pivot member 119 is incorporated therein. A compressivetorsion spring 120 which is a bias member is further incorporated intothe pivot member 119. Due to the action of the incorporated compressivetorsion spring 120, a rotative force in a clockwise direction withrespect to the X-axis is applied to the lens retention frame 116 throughthe pivot member 119. Furthermore, the pivot member 119 is supported byan engaging hole 116 d of the lens retention frame 116 whilepressurizing the fitting hole to absorb the rattle of the movable part,and the pivot member 119 can be moved forward and backward in the X-axisdirection integrally with the lens retention frame.

FIG. 4A and FIG. 4B are sectional views of an essential part of thelinear ultrasonic motor to which the lens retention frame is connected;FIG. 4A illustrates a YZ cross section including the center of thespring 108 in FIG. 2; and FIG. 4B illustrates the sectional view takenalong the line 4B-4B in FIG. 4A.

In an incorporated state, an engaging part 119 a of the V-shaped groovewhich is a concave portion provided in the pivot member 119 isincorporated into the linear ultrasonic motor so as to be engaged withthe transmission part 104 a which is integrally formed in the vibratorsupport member 104 and has a convex shape with a spherical surfaceshape, and the transmission part 104 a with the spherical surface shapeand the engaging part 119 a of the V-shaped groove form a point contact(partial contact), because both the parts are engaged with each other.Thus, the transmission mechanism in the present exemplary embodiment,which transmits the driving force of the linear ultrasonic motor to thelens retention frame of the body to be driven, has a structure forbiasing the transmission member including the pivot member against thetransmission part provided in the movable part by the bias member tomake the members engaged with each other by the friction. Incidentally,the shape of the engaging part 119 a is not limited to the V-shapedgroove, and may be another shape as long as the engaging part 119 aforms the above described point contact. In addition, in the abovedescription, a structure has been described in which the transmissionpart with the convex shape is engaged with the engaging part with theconcave shape of the transmission member, but the engaging part of thetransmission member with the convex shape can also be structured so asto be engaged with the transmission part with the concave shape. Each ofthe linear ultrasonic motor 100, the guide bar 117 and the steady bracebar 118 is fixed to a not-shown lens barrel base member.

In addition, the spring 108 pressurizes the pressurization plate 105through the spring retention member 107. This pressurization forcebiases the vibrator 103 against the contact base member 115 through theelastic member 106 (Fa in the figure).

A reaction force Fb of the pressurization force Fa is transmitted to therolling part from the vibrator support member 104 through the movingplate 110. The rolling part is interposed between the moving plate 110and the cover plate 112. Here, when the value of the reaction force Fbis large, a frictional force generated when the vibrator support member104 is driven in the X-axis direction results in being large. However,in the present exemplary embodiment, the rolling part is interposedbetween the V-shaped grooves, the vibrator support member 104 is held soas to be guided straight, and there is no sliding part, which reduces adriving loss of the movable part.

In addition, the compressive torsion spring 120 biases the pivot member119 against the transmission part 104 a which is formed integrally withthe vibrator support member 104 (Fc in the figure). The vibrator supportmember 104 and the pivot member 119 are held by friction due to thispressurization force, and the driving force of the movable part to theX-axis direction is transmitted to the lens retention frame 116.

On the other hand, there is the case where an error occurs between theaccuracy in guiding the movable part straight in the X-axis directionand the accuracy in guiding the lens retention frame 116 straight. Atthis time, an equalizing mechanism becomes necessary which equalizes theerrors of the accuracies in straight-ahead guiding between thetransmission part 104 a and the pivot member 119. On the other hand, inthe present exemplary embodiment, the pivot member 119 has the engagingpart 119 a which has a V groove shape, and holds the transmission part104 a without causing rattle in the X-axis direction. In addition, inthe Y-axis direction in the figure, the pivot member 119 is formed so asto have an aperture-shaped part. In addition, it is necessary to slidethe transmission part 104 a and the pivot member 119 by low friction, inorder to prevent wrenching between the vibrator support member 104 andthe lens retention frame 116. Because of this, the pivot member 119 isdesirably molded from a high-sliding material such as POM (polyacetal).In addition, it is desirable to subject the surface of the transmissionpart 104 a to mirror finish to lower sliding resistance, or to fix ahard ball which is made of ceramic, stainless steel, brass, tungstencarbide, carbon steel or the like, with an adhesive or the like.

In the present constitution, a biasing direction (Fc) of the compressivetorsion spring 120 to the transmission part 104 a is the same directionas the reaction force Fb of the pressurization force Fa of the spring108 (that is, the opposite direction to the pressurization direction).In other words, the biasing force of the rolling part to the cover plate112 becomes a resultant force of Fb and Fc. Because of this, the rattleof the movable part is reduced, and the straight-ahead stability of themovable part to the X-axis direction is enhanced. In other words, boththe biasing force Fc due to the compressive torsion spring 120 and thepressurization force Fa against the vibrator 103 have stronger forces inthe direction perpendicular to the movable direction than in the movabledirection (X-axis direction), and the biasing force Fc due to thecompressive torsion spring 120 has a stronger force in the directionthat is perpendicular to the pressurization direction against thevibrator 103 than in the direction perpendicular to the pressurizationdirection (Z-axis direction).

In addition, the transmission part 104 a, the movable guide part of theV-shaped groove in the moving plate 110, and the cover guide part havingthe V-shaped groove of the cover plate 112, are arranged on the Z-axisso as to coincide with the others. In other words, the rolling part andthe transmission part are arranged so as to match in the Z-axisdirection when being projected onto a YZ plane, or the rolling part andthe transmission part are arranged so as to be arrayed in a movingdirection (X-axis direction) of the movable part. Due to the presentarrangement, a moment disadvantageous and unnecessary for thestraight-ahead stability of the vibrator support member 104 does notoccur, which can enhance a transmission efficiency of the driving force.

As described above, the present exemplary embodiment enables the linearultrasonic motor to efficiently provide the driving force even when thepressurization force of the vibrator is increased.

FIG. 5 illustrates a lens barrel, as one example of a lens apparatusinto which a linear ultrasonic motor 100 of the present invention isincorporated.

Incidentally, because the lens barrel has a shape of approximatelyrotational symmetry, only the upper half is illustrated.

A lens barrel 2 is detachably mounted on a camera body 1 of an imagepickup apparatus, and an imaging device 1 a is provided in the camerabody 1. A mount 11 of the camera body 1 has a bayonet part for mountingthe lens barrel 2 on the camera body 1. The lens barrel 2 has a fixingcylinder 12, and abuts on a flange part of the mount 11. The fixingcylinder 12 and the mount 11 are fixed by a not-shown screw.Furthermore, a front lens barrel 13 for holding a lens G1 and a rearlens barrel 14 for holding a lens G3 are fixed to the fixing cylinder12. The lens barrel 2 further includes a focal lens retention frame 116which holds a lens G2. The focal lens retention frame 116 is furtherheld by the guide bar 117 which is held by the front lens barrel 13 andthe rear lens barrel 14, so as to be capable of moving straight. Anot-shown flange part is formed on the base member 114 of the ultrasonicmotor 100, and is fixed to the rear lens barrel 14 by a screw or thelike.

When the movable part including the vibrator support member 104 of theultrasonic motor 100 is driven in the above described structure, thedriving force of the ultrasonic motor 100 is transmitted to the lensretention frame 116 through the vibrator support member 104. The lensretention frame 116 is guided by the guide bar 117 to linearly move.

Exemplary Embodiment 2

FIG. 6 is a sectional view of an essential part of a linear ultrasonicmotor which is a second exemplary embodiment of the present invention.The reference numerals of members having functions which overlap withthose in the first exemplary embodiment shall be common in the presentfigure. In addition, the descriptions concerning contents of which thestructures and functions are common with those in the first exemplaryembodiment will be omitted.

In the first exemplary embodiment, the transmission part provided on thevibrator support member 104 and the pivot member 119 are structured soas to be engaged with each other. On the other hand, the presentexemplary embodiment is structured so that the transmission part 107 aof the spring retention member 107, which penetrates through the springkeep plate and extends to the outside, is provided in the springretention member 107, and the pivot member 119 is engaged with thetransmission part 107 a of the spring retention member 107, in theextending end. As for the detail, in the state in which the linearultrasonic motor 200 is incorporated into a not-shown lens barrel, theengaging part 119 a of the V-shaped groove in the pivot member 119 whichis held by the lens barrel is incorporated into the linear ultrasonicmotor so as to be engaged with the transmission part 107 a that isformed integrally with the spring retention member 107 and has aspherical surface shape. The transmission part 107 a of the springretention member 107, which has the convex shape with the sphericalsurface shape, is engaged with the engaging part 119 a of the V-shapedgroove, which is a concave portion, provided in the pivot member 119,and thereby both the parts form a point contact (partial contact).Incidentally, the shape of the engaging part 119 a is not limited to theV-shaped groove, and may be another shape as long as the above describedpoint contact is formed.

The spring 108 pressurizes the pressurization plate 105 through thespring retention member 107. This pressurization force biases thevibrator 103 against the contact base member 115 through the elasticmember 106 (Fa in the figure).

The reaction force Fb of the pressurization force Fa is transmitted tothe rolling members (rolling balls) 111 which correspond to a rollingpart from the vibrator support member 104 through the moving plate 110.The rolling part is interposed between the respective guide parts of themoving plate 110 and the cover plate 112.

A not-shown compressive torsion spring biases the pivot member 119against the transmission part 107 a which is formed integrally with thespring retention member 107 (Fc in the figure). The spring retentionmember 107 and the pivot member 119 are held by friction due to thispressurization force, and the driving force of the movable part to theX-axis direction is transmitted to a not-shown lens retention frame.

In the present structure, a biasing direction (Fc) of the not-showncompressive torsion spring to the transmission part 107 a is the samedirection as the pressurization force Fa of the spring 108 (that is, thepressurization direction). In other words, the biasing force of thetorsion spring exists on the same axis line as the pressurization forceFa. Accordingly, the pressurization force to the pressurization plate105 becomes a resultant force of Fa and Fc. Here, when a necessarypressurization force to the pressurization plate 105 can be obtainedonly by the pressurization force Fc, the spring 108 may be eliminatedfrom the structure. Here, the biasing force Fb of the rolling partagainst the cover plate 112 becomes a reaction force of a resultantforce of the pressurization forces Fa and Fc. Here, the engaging part119 a of the V-shaped groove in the pivot member 119, the transmissionpart 107 a of the spring retention member 107 and the contact part 101 aof the vibration plate 101 are arranged on the Z-axis so as to coincidewith the others in a projection onto the YZ plane. Alternatively, thetransmission part 107 a and the contact part 101 a are arranged so as tobe arrayed or match in the moving direction of the movable part. Inother words, a thrust generating part which generates an ellipsoidalmotion and the transmission part which transmits the driving force arearranged so as to match in an XZ plane, which accordingly canefficiently transmit a thrust of the movable body. In other words, boththe biasing force Fc due to the compressive torsion spring and thepressurization force Fa against the vibrator 103 have stronger forces inthe direction perpendicular to the movable direction than in the movabledirection (X-axis direction), and the biasing force Fc due to thecompressive torsion spring has a stronger force in the direction that isperpendicular to the pressurization direction against the vibrator 103than in the direction perpendicular to the pressurization direction(Z-axis direction).

Exemplary Embodiment 3

FIG. 7 is a sectional view of an essential part of a linear ultrasonicmotor which is a third exemplary embodiment of the present invention.The reference numerals of members having functions which overlap withthose in the first exemplary embodiment shall be common in the presentfigure. In addition, the descriptions concerning contents of which thestructures and functions are common with those in the first exemplaryembodiment will be omitted.

In the first exemplary embodiment, the vibrator support member 104 andthe pivot member 119 have been structured so as to be engaged with eachother on the side face portion of the vibrator support member 104. Incontrast, in the structure of the linear ultrasonic motor 300 accordingto the embodiment, only the arrangement of the transmission part 104 ais different that is formed integrally with the vibrator support member104 of the linear ultrasonic motor 100 and has a spherical surfaceshape, which has been described in the first exemplary embodiment.Specifically, in the present exemplary embodiment, the vibrator supportmember 104 and the pivot member 119 are structured so as to be engagedwith each other on the bottom face portion of the vibrator supportmember 104.

In the present structure, a biasing direction (Fc) of a not-showncompressive torsion spring to the transmission part 104 a is the samedirection as the reaction force Fb of the pressurization force Fa of thespring 108 (that is, the opposite direction to the pressurizationdirection). In other words, the biasing force of the rolling partincluding the rolling members (rolling balls) 111 a, 111 b and 111 c tothe cover plate 112 becomes a resultant force of Fb and Fc. Because ofthis, the rattle of the movable part is reduced, and the straight-aheadstability of the movable part to the X-axis direction is enhanced.Furthermore, the engaging part 119 a of the V-shaped groove in the pivotmember 119, the transmission part 104 a of the vibrator support member104 and the contact part 101 a of the vibration plate 101 are arrangedso as to be arrayed or match in the advancing direction of the movablepart. In other words, a thrust generating part (contact part) whichgenerates an ellipsoidal motion and the transmission part are arrangedso as to match in the XZ plane, which accordingly can efficientlytransmit a thrust of the movable body. In other words, both the biasingforce Fc due to the compressive torsion spring and the pressurizationforce Fa against the vibrator 103 have stronger forces in the directionperpendicular to the movable direction than in the movable direction(X-axis direction), and the biasing force Fc due to the compressivetorsion spring has a stronger force in the direction that isperpendicular to the pressurization direction against the vibrator 103than in the direction perpendicular to the pressurization direction(Z-axis direction).

Exemplary Embodiment 4

FIG. 8 is a side view of a linear ultrasonic motor 400 when viewed froma Y-axis direction, which is a fourth exemplary embodiment of thepresent invention, and a movable part is in a middle position.

FIG. 9 illustrates an exploded perspective view of the linear ultrasonicmotor.

Firstly, the structure of the linear ultrasonic motor 400 of the presentexemplary embodiment will be described below with reference to FIG. 8and FIG. 9. Incidentally, the reference numerals of members havingfunctions which overlap with those in the first exemplary embodimentshall be common in the present figure. In addition, the descriptionsconcerning contents of which the structures and functions are commonwith those in the first exemplary embodiment will be omitted.

The linear ultrasonic motor 400 in the present exemplary embodiment hasa longitudinal axis in an X-axis direction, and is formed of each memberwhich will be described below. The vibration plate 101 has thepiezoelectric element 102 fixed thereon by a well-known adhesive or thelike. The vibration plate 101 further includes a contact part 101 a, andthe contact part 101 a comes in contact with a straight-ahead movingplate 401 which will be described later, under a pressurized contactcondition that entails pressurization. The vibrator 103 is formed of thevibration plate 101 and the piezoelectric element 102.

A vibrator support member 104 has a convex shape in the Z-axis directionof a YZ cross section, and includes a through hole for receiving aspring 108 and a spring retention member 107 therein. The springretention member 107 has a face for receiving and holding one end of thespring 108, and the back side of the face comes in surface contact withthe pressurization plate 105. The other end of the spring comes incontact with a spring keep plate 109, and the spring keep plate 109 canbe fitted into the through hole of the vibrator support member 104. Inthe through hole, the spring 108 is held by the spring retention member107, and is interposed between the pressurization plate 105 and thespring keep plate 109. Thereby, the spring 108 can freely expand andcontract, and applies a pressurization force to the Z-axis direction. Inaddition, the pressurization plate 105 has two projecting portions on aface of a side which receives the spring retention member 107, in adirection parallel to the normal direction of the face. The twoprojecting portions are received in the holes provided in the vibratorsupport member 104, respectively. The movement to directions other thanthe Z-axis direction is limited by this structure, and thepressurization force is efficiently transmitted to other members. In thepresent exemplary embodiment, the pressurization plate 105, the springretention member 107, the spring 108 and the spring keep plate 109constitute a pressurization member, and the centers of gravity of eachcomponent can be connected by a straight line parallel to the Z-axis.

An elastic member 106 is arranged between the piezoelectric element 102and the pressurization plate 105.

The straight-ahead moving plate 401 includes three movable guide parts401 a, 401 b and 401 c of a V-shaped groove, and the movable guide parts401 a, 401 b and 401 c of the V-shaped groove extend with apredetermined length in the X-axis direction. In addition, thestraight-ahead moving plate 401 includes a transmission part 401 d whichis engaged with the pivot member 119 that will be described later.

On the other hand, a base member 402 also includes three base memberguide parts 402 a, 402 b and 402 c of a V-shaped groove which extendswith a predetermined length in the X-axis direction, and sphericalrolling members (rolling balls) 111 a, 111 b and 111 c which correspondto a rolling part are rotatably interposed between the base member guideparts 402 a, 402 b and 402 c of the V-shaped groove and the movableguide parts 401 a, 401 b and 401 c of the V-shaped groove, whichcorrespond to the base member guide parts, respectively. Incidentally,the shape of the movable guide parts 401 a, 401 b and 401 c and the basemember guide parts 402 a, 402 b and 402 c is not limited to the V-shapedgroove, and may be another shape as long as the rolling part can berotatably interposed therebetween.

The straight-ahead moving plate 401 comes in contact with the contactpart 101 a of the vibration plate 101, and an ellipsoidal motion whichis generated in the vibrator 103 is converted into a driving force ofthe movable part by the friction therebetween. The movable part can moveforward and backward in the X-axis direction by the driving force. Inthe present exemplary embodiment, the base part is formed of thevibrator 103, the elastic member 106, the pressurization plate 105, thevibrator support member 104, the spring retention member 107, the spring108, the spring keep plate 109 and the base member 402, and the movablepart is formed of the straight-ahead moving plate 401.

Hereinafter, the pressurization force which is generated in thepressurization member will be described below. The spring 108 appliesthe pressurization force to the pressurization plate 105 through thespring retention member 107. The pressurization force furtherpressurizes the vibrator 103 to the straight-ahead moving plate 401through the elastic member 106, and the vibrator 103 is biased to thestraight-ahead moving plate 401. The contact part 101 a of the vibrationplate 101 comes in contact with the straight-ahead moving plate 401 in astate of being pressurized against the straight-ahead moving plate. Thepressurization force to the straight-ahead moving plate 401 is receivedby the base member 402 through the rolling part. When voltage is appliedto the piezoelectric element 102 under this pressurized contactcondition, the resonances in each of the X-axis direction and the Y-axisdirection occur in the vibrator 103, and the tip of the contact part 101a causes the ellipsoidal motion. As a result, the movable part can moveforward and backward in the X-axis direction.

FIG. 10 is a sectional view of an essential part of the linearultrasonic motor to which the lens retention frame is connected.

In the incorporated state, the engaging part 119 a of the V-shapedgroove, which is a concave portion provided in the pivot member 119, isincorporated into the linear ultrasonic motor so as to be engaged withthe transmission part 401 d which is formed integrally with thestraight-ahead moving plate 401 and has a spherical convex shape, andthe engaging part and the transmission part form a point contact.Incidentally, the shape of the engaging part 119 a is not limited to theV-shaped groove, and may be another shape as long as the above describedpoint contact is formed.

In addition, the spring 108 pressurizes the pressurization plate 105through the spring retention member 107. This pressurization forcebiases the vibrator 103 against the straight-ahead moving plate 401through the elastic member 106 (Fa in the figure). Here, when the valueof the pressurization force Fa is large, a frictional force generatedwhen the straight-ahead moving plate 401 is driven in the X-axisdirection results in being large. However, in the present exemplaryembodiment, the rolling part is interposed between the V-shaped grooves,the straight-ahead moving plate 401 is held so as to be guided straight,and there is no sliding part, which reduces a driving loss of themovable part.

In addition, the compressive torsion spring 120 biases the pivot member119 against the transmission part 401 d which is formed integrally withthe straight-ahead moving plate 401 (Fc in the figure). The transmissionpart 401 d of the straight-ahead moving plate 401 and the pivot member119 are held by friction due to this pressurization force, and thedriving force of the movable part to the X-axis direction is transmittedto the lens retention frame 116.

In the structure of the present exemplary embodiment, a biasingdirection (Fc) of the compressive torsion spring 120 to the transmissionpart 401 d is the same direction as the pressurization force Fa of thespring 108 (that is, the pressurization direction). In other words, thebiasing force of the rolling part to the base member 402 becomes aresultant force of Fa and Fc. Because of this, the rattle of the movablepart is reduced, and the straight-ahead stability of the movable part tothe X-axis direction is enhanced. In other words, both the biasing forceFc due to the compressive torsion spring 120 and the pressurizationforce Fa against the vibrator 103 have stronger forces in the directionperpendicular to the movable direction than in the movable direction(X-axis direction), and the biasing force Fc due to the compressivetorsion spring 120 has a stronger force in the direction that isperpendicular to the pressurization direction against the vibrator 103than in the direction perpendicular to the pressurization direction(Z-axis direction).

Up to this point, specific examples concerning the linear ultrasonicmotor according to the present invention have been described in detail,but the present invention is not limited to the above describedexemplary embodiments, and can have any form as long as the form isdescribed in the scope of the claims.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2013-076194, filed Apr. 1, 2013, and Japanese Patent Application No.2014-058095, filed Mar. 20, 2014, which are hereby incorporated byreference herein in their entirety.

1.-45. (canceled)
 46. A driving apparatus comprising: a vibrator, thevibrator having a piezoelectric element; a movable part, the movablepart applying a pressing force to the vibrator and bringing the vibratorinto pressed contact with a base part, the movable part having atransmission part and a movable guide part; a cover part, the cover partbeing fixed to the base part and having a cover guide part; a rollingpart being rollably held between the movable guide part of the movablepart and the cover guide part of the cover part, the movable guide partextending in a movable direction and the cover guide part extending inthe movable direction; and a body to be driven, the body to be drivenhaving a transmission member that is pivotably supported and able tomove only in the movable direction, wherein the transmission membercomprises a bias part that abuts on the transmission part of the movablepart and applies a biasing force of biasing the movable part to therolling part to the transmission part, and the rolling part is held by aresultant force of the pressing force or a reaction force of thepressing force, and the biasing force.
 47. The driving apparatusaccording to claim 46, wherein the rolling part and the transmissionpart are arranged so as to be arrayed in a direction of the pressingforce, when projected onto a plane perpendicular to the movabledirection.
 48. The driving apparatus according to claim 46, wherein thevibrator has a contact part, the contact part coming in contact with thebase part, and the transmission part is arranged so as to be arrayed ormatch with the contact part in a moving direction of the movable part.49. The driving apparatus according to claim 46, wherein thetransmission part is arranged so as to be arrayed or match with therolling part in the movable direction.
 50. The driving apparatusaccording to claim 46, wherein the transmission part of the movable parthas a convex shape, and is engaged with a concave portion provided inthe transmission member.
 51. The driving apparatus according to claim46, wherein the transmission part has a spherical surface shape formedintegrally with the movable part, and comes in point contact with thetransmission member.
 52. The driving apparatus according to claim 51,wherein the transmission part is formed from a hard ball, the hard ballbeing made of one of ceramic, stainless steel, brass, tungsten carbideand carbon steel.
 53. The driving apparatus according to claim 46,wherein the bias part comprises a torsion spring.
 54. The drivingapparatus according to claim 46, wherein the rolling part is formed of aspherical rolling ball.
 55. The driving apparatus according to claim 46,wherein the body to be driven comprises a lens retention frame.
 56. Alens apparatus comprising the driving apparatus according to claim 55,and a guide bar, the guide bar guiding the lens retention frame.
 57. Thelens apparatus according to claim 56, further comprising a steady bracebar, the steady brace bar extending in the same direction as the guidebar and preventing a rotation of the lens retention frame due to thebiasing force of the bias part.
 58. An image pickup apparatus comprisingthe lens apparatus according to claim
 56. 59. The driving apparatusaccording to claim 46, wherein the driving apparatus comprises a linearultrasonic motor in which the piezoelectric element causes an ultrasonicvibration.
 60. A driving apparatus comprising: a movable part that movesby vibration of a vibrator having a piezoelectric element configured tocause the vibration; a base part, a guide mechanism, the guide mechanismmovably guiding the movable part with respect to the base part in amovable direction; and a transmission mechanism, the transmissionmechanism transmitting a movement of the movable part to a body to bedriven, wherein the vibrator is configured to be pressed to come incontact with the base part or the movable part, the transmissionmechanism comprises a transmission member transmits a driving force ofthe driving apparatus due to the movement of the movable part to thebody to be driven, and a bias member that applies a biasing force thatbiases the transmission member to the movable part, and a transmissionpart of the movable part is biased in a pressing direction of thevibrator against the base part or the movable part, or in the reversedirection, through the transmission member, by the biasing force due tothe bias member, the transmission member is engaged with thetransmission part of the movable part, and the driving force istransmitted to the body to be driven.
 61. The driving apparatusaccording to claim 60, wherein the guide mechanism comprises a rollingmember, the rolling member movably guiding the movable part with respectto the base part.
 62. The driving apparatus according to claim 61,wherein the transmission part is arranged so as to be arrayed or matchwith the rolling member in the movable direction.
 63. The drivingapparatus according to claim 61, wherein the rolling member is formed ofa spherical rolling ball and the rolling ball is interposed between aguide part provided in the movable part and a guide part provided in thebase part.
 64. The driving apparatus according to claim 60, wherein thevibrator has a contact part, the contact part coming in contact with thebase part, and the transmission part is arranged so as to be arrayed ormatch with the contact part in the movable direction.
 65. The drivingapparatus according to claim 60, wherein the transmission part of themovable part has a convex shape and is engaged with a concave portionprovided in the transmission member.
 66. The driving apparatus accordingto claim 60, wherein the vibrator is pressed by a pressing member andcomes in contact with the base part or the movable part.
 67. The drivingapparatus according to claim 66, wherein the base part comprises acontact base member and the vibrator is pressed by the pressing memberand comes in contact with the contact base member.
 68. The drivingapparatus according to claim 66, wherein the vibrator is pressed by thepressing member and comes in contact with the movable part.
 69. Thedriving apparatus according to claim 60, wherein the transmission partis formed from a hard ball, the hard ball being made of one of ceramic,stainless steel, brass, tungsten carbide and carbon steel.
 70. Thedriving apparatus according to claim 60, wherein the bias membercomprises a torsion spring.
 71. The driving apparatus according to claim60, wherein the body to be driven comprises a lens retention frame. 72.A lens apparatus comprising the driving apparatus according to claim 71,and a guide bar, the guide bar guiding the lens retention frame.
 73. Thelens apparatus according to claim 72, further comprising a steady bracebar, the steady brace bar extending in the same direction as the guidebar and preventing a rotation of the lens retention frame due to thebiasing force of the bias member.
 74. An image pickup apparatuscomprising the lens apparatus according to claim
 72. 75. A drivingapparatus comprising: a movable part that includes a vibrator having apiezoelectric element configured to cause vibration; a guide part, theguide part movably guiding the movable part with respect to a base partin a movable direction by the vibration of the vibrator; and atransmission member, the transmission member coming in contact with themovable part by receiving a biasing force due to a bias member, andtransmitting a driving force due to a movement of the movable part withrespect to the base part to a body to be driven by the contact, whereinthe vibrator is configured to be pressed to come in contact with thebase part, and both the biasing force due to the bias member and apressing force against the vibrator have stronger forces in a directionperpendicular to the movable direction than in the movable direction,and the biasing force due to the bias member has a stronger force in adirection that is perpendicular to a pressing direction against thevibrator than in a direction perpendicular to the pressing direction.76. The driving apparatus according to claim 75, wherein the force inthe direction of the biasing force is stronger in the directionperpendicular to the movable direction than in the movable direction.77. The driving apparatus according to claim 75, wherein the force inthe direction of the pressing force against the vibrator is stronger inthe direction perpendicular to the movable direction than in the movabledirection.
 78. The driving apparatus according to claim 75, wherein theguide part comprises a rolling member, the rolling member movablyguiding the movable part with respect to the base part.
 79. The drivingapparatus according to claim 78, wherein the rolling member is formed ofa spherical rolling ball and the rolling ball is interposed between aguide part provided in the movable part and a guide part provided in thebase part.
 80. The driving apparatus according to claim 75, wherein thevibrator has a contact part, the contact part coming in contact with thebase part, and the transmission part is arranged so as to be arrayed ormatch with the contact part in the movable direction.
 81. The drivingapparatus according to claim 80, wherein the transmission member isarranged so as to be arrayed or match with the rolling member in themovable direction.
 82. The driving apparatus according to claim 75,wherein the transmission part with the convex shape provided in themovable member is engaged with a concave portion provided in thetransmission member.
 83. The driving apparatus according to claim 82,wherein the transmission part of the movable part, contacting thetransmitting member, is formed from a hard ball, the hard ball beingmade of one of ceramic, stainless steel, brass, tungsten carbide andcarbon steel.
 84. The driving apparatus according to claim 75, whereinthe vibrator comes in contact with the base part with the pressing forcebeing generated by a pressing member.
 85. The driving apparatusaccording to claim 84, wherein the base part comprises a contact basemember and the vibrator is pressed by the pressing member and comes incontact with the contact base member.
 86. The driving apparatusaccording to claim 84, wherein the vibrator comes in contact with thebase part via the pressing member.
 87. The driving apparatus accordingto claim 75, wherein the bias member comprises a torsion spring.
 88. Thedriving apparatus according to claim 74, wherein the body to be drivencomprises a lens retention frame.
 89. A lens apparatus comprising thedriving apparatus according to claim 88, and a guide bar, the guide barguiding the lens retention frame.
 90. The lens apparatus according toclaim 89, further comprising a steady brace bar, the steady brace barextending in the same direction as the guide bar and preventing arotation of the lens retention frame due to the biasing force of thebias member.
 91. An image pickup apparatus comprising the lens apparatusaccording to claim 89.